Semiconductor light-emitting devices

ABSTRACT

A semiconductor light-emitting device includes a substrate having an upper surface and a plurality of bumps positioned on the upper surface, a first conductive type semiconductor layer positioned on the substrate, a light-emitting structure positioned on the first conductive type semiconductor layer, and a second conductive type semiconductor layer positioned on the light-emitting structure. In one embodiment of the present disclosure, each of the bumps has a top plane substantially parallel to the upper surface, the first conductive type semiconductor layer has a plurality of protrusions each facing a portion of the substrate between the bumps, and the protrusions are spaced apart from the bumps.

BACKGROUND OF THE INVENTION

(A) Field of the Invention

The present disclosure relates to a semiconductor light-emitting device,and more particularly, to a semiconductor light-emitting device withlight-extraction efficiency improved by forming bumps having a top planesubstantially parallel to the upper surface of the substrate and a firstconductive type semiconductor layer having protrusions each facing aportion of the substrate between the bumps and spaced apart from thebumps.

(B) Description of the Related Art

Semiconductor light-emitting devices such as light-emitting diodes (LED)have been widely used in traffic lights, vehicle electronics, LCDbacking lights, and general illumination. In the light-emitting diode ann-type semiconductor layer, a light-emitting region and a p-typesemiconductor layer are essentially made to grow on a substrate to forma layered structure, and the electrodes are formed on the p-typesemiconductor layer and on the n-type semiconductor layer. Light isgenerated through the recombination of holes and electrons that havebeen injected through the semiconductor layers to the light-emittingregion, and then emitted through a light transmitting electrode on thep-type semiconductor layer or from the substrate. The material used forpreparing the visible light-emitting diode includes the III-V compoundsuch as AlGaInP for green, yellow, orange or red light-emitting diodes,and GaN for blue or ultraviolet light-emitting diodes, wherein the GaNlight-emitting diode is formed on the sapphire substrate.

Extracting the light beams generated by the light-emitting layer to theoutside of the light-emitting device is one important issue to beimproved in the semiconductor light-emitting device. Researchers use atransparent electrode in the conventional light-emitting device toprevent the upward light beams generated by the light-emitting layerfrom being blocked on the propagation path to the outside of thelight-emitting device, or use a reflection layer to reflect the downwardlight beams generated by the light-emitting layer back to the top of thelight-emitting device. However, in addition to the upward light beamsand downward light beams, the light-emitting layer also emits lightbeams in other directions, and a portion of the light beams arereflected internally into the light-emitting device due to the totalreflection effect. Consequently, the light beams may be adsorbed by thelight-emitting layer, rather than propagating to the outside of thelight-emitting device.

TW 561632 discloses a semiconductor light-emitting device having atleast one recess and/or protruding portion on the surface portion of asubstrate. The recess and/or protruding portion has a shape thatprevents crystal defects from occurring in semiconductor layers. Inaddition, TW 536841 discloses a semiconductor light-emitting elementhaving an undulation formed on the surface of a first layer (substrate),and a second layer having a refractory index different from that of thefirst layer grown to fill the undulation. Furthermore, a first crystalmay be grown in an undulated shape on a crystal layer, which is thefoundation of crystal growth. After such undulated refractory interfaceis formed, a semiconductor crystal layer having a refractory indexdifferent from that of the first layer is laminated thereon.

SUMMARY OF THE INVENTION

One aspect of the present disclosure provides a semiconductorlight-emitting device with improved light-extraction efficiency byforming bumps having a top plane substantially parallel to the uppersurface of the substrate and a first conductive type semiconductor layerhaving protrusions each facing a portion of the substrate between thebumps and spaced apart from the bumps.

A semiconductor light-emitting device according to this aspect of thepresent disclosure comprises a substrate including an upper surface anda plurality of bumps positioned on the upper surface, a first conductivetype semiconductor layer positioned on the substrate, a light-emittingstructure positioned on the first conductive type semiconductor layer,and a second conductive type semiconductor layer positioned on thelight-emitting structure. In one embodiment of the present disclosure,each of the bumps includes a top plane substantially parallel to theupper surface, the first conductive type semiconductor layer includes aplurality of protrusions each facing a portion of the substrate betweenthe bumps, and the protrusions are spaced apart from the bumps.

The foregoing has outlined rather broadly the features and technicaladvantages of the present disclosure in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter, which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures or processes for carrying outthe same purposes of the present disclosure. It should also be realizedby those skilled in the art that such equivalent constructions do notdepart from the spirit and scope of the invention as set forth in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The objectives and advantages of the present disclosure will becomeapparent upon reading the following description and upon reference tothe accompanying drawings in which:

FIG. 1 is a top view of a semiconductor light-emitting device accordingto a first embodiment of the present disclosure;

FIG. 2 is a cross-sectional view along the line 1-1 in FIG. 1;

FIG. 3 is a top view of the substrate according to the first embodimentof the present disclosure;

FIG. 4 is a scanning electron microscopy image of the substrateaccording to the first embodiment of the present disclosure;

FIG. 5 is a close-up cross-sectional view along the line 1-1 in FIG. 1according to one embodiment of the present disclosure;

FIG. 6 is a close-up cross-sectional view along the line 2-2 in FIG. 1according to one embodiment of the present disclosure;

FIG. 7 is a scanning electron microscopy image on the close-up area;

FIG. 8 is a close-up cross-sectional view along the line 1-1 in FIG. 1according to another embodiment of the present disclosure;

FIG. 9 is a close-up cross-sectional view along the line 2-2 in FIG. 1according to another embodiment of the present disclosure;

FIG. 10 is a top view of a semiconductor light-emitting device accordingto a second embodiment of the present disclosure;

FIG. 11 is a cross-sectional view along the line 3-3 in FIG. 10;

FIG. 12 is a full view of the substrate of the semiconductorlight-emitting device of FIG. 10.

FIG. 13 is a close-up cross-sectional view along the line 3-3 in FIG. 10according to one embodiment of the present disclosure;

FIG. 14 is a close-up cross-sectional view along the line 4-4 in FIG. 10according to one embodiment of the present disclosure;

FIG. 15 is a close-up cross-sectional view along the line 3-3 in FIG. 10according to another embodiment of the present disclosure;

FIG. 16 is a close-up cross-sectional view along the line 4-4 in FIG. 10according to another embodiment of the present disclosure;

FIG. 17 is a top view of a semiconductor light-emitting device accordingto a third embodiment of the present disclosure;

FIG. 18 is a cross-sectional view along the line 5-5 in FIG. 17;

FIG. 19 is a full view of the substrate according to the thirdembodiment of the present disclosure;

FIG. 20 is a scanning electron microscopy image of the substrateaccording to the third embodiment of the present disclosure;

FIG. 21 is a close-up cross-sectional view along the line 5-5 in FIG. 17according to one embodiment of the present disclosure;

FIG. 22 is a close-up cross-sectional view along the line 6-6 in FIG. 17according to one embodiment of the present disclosure;

FIG. 23 is a close-up cross-sectional view along the line 5-5 in FIG. 17according to another embodiment of the present disclosure; and

FIG. 24 is a close-up cross-sectional view along the line 6-6 in FIG. 17according to another embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a top view of a semiconductor light-emitting device 10according to a first embodiment of the present disclosure, and FIG. 2 isa cross-sectional view along the cross-sectional line 1-1 in FIG. 1. Thesemiconductor light-emitting device 10 comprises a substrate 12 having aplurality of bumps 30, an n-type semiconductor layer 14 positioned onthe substrate 12, a light-emitting structure 16 positioned on the n-typesemiconductor layer 14, a p-type semiconductor layer 18 positioned onthe light-emitting structure 16, a contact layer 20 positioned on thep-type semiconductor layer 18, a transparent conductive layer 22positioned on the contact layer 20, a first electrode 24 positioned onthe n-type semiconductor layer 14, and a second electrode 26 positionedon the transparent conductive layer 22.

FIG. 3 is a top view of the substrate 12 according to the firstembodiment of the present disclosure, and FIG. 4 is a scanning electronmicroscopy image of the substrate 12 according to the first embodimentof the present disclosure. In one embodiment of the present disclosure,the substrate 12 has an upper surface 12A with the bumps 30 positionedon the upper surface 12A in a periodic manner. The bumps 30 arepositioned in a plurality of odd rows and a plurality of even rows, andeach of the bumps 30 in the even rows is positioned at an intervalbetween adjacent two bumps 30 in the odd rows. The height of the bumps30 is between 0.5 and 5 microns, the interval between the adjacent twobumps 30 is between 0.5 and 10 microns, and the width of the bumps 30 isbetween 0.5 and 5 microns.

Each bump 30 has a top plane 32, three wall surfaces 34, and threeinclined surfaces 36 sandwiched between the top plane 32 and the wallsurfaces 34, wherein each of the inclined surfaces 36 is between two ofthe wall surfaces 36. The wall surfaces 34 and the inclined surfaces 36of the bump 30 have different inclined angles, which is the includedangle between the upper surface 12A and the wall surface 34 (or theinclined surface 36). The wall surface 34 and the inclined surface 36are connected, and the included angle between the inclined surface 36and the wall surface 34 is between 90 and 180 degrees. In addition, thebump 30 has a base surface 38 having three corners, and the connectionof the corners is arc-shaped, i.e., the wall surface 34 is arc-shaped.

FIG. 5 is a close-up cross-sectional view along the cross-sectional line1-1 in FIG. 1, FIG. 6 is a close-up cross-sectional view along thecross-sectional line 2-2 in FIG. 1, and FIG. 7 is a scanning electronmicroscopy image on the close-up area according to one embodiment of thepresent disclosure. In one embodiment of the present disclosure, thefirst conductive type semiconductor layer 14 includes a plurality ofprotrusions 44 each facing a portion of the upper surface 12A of thesubstrate 12 between the bumps 30. Furthermore, the first conductivetype semiconductor layer 14 may optionally include a plurality ofprojections 42 each facing the top plane 32 of the bumps 30. In oneembodiment of the present disclosure, the protrusions 44 are positionedin a ring manner at a peripheral region 40 of the first conductive typesemiconductor layer 14, and the width of the peripheral region 40 isbetween 5 and 10 microns, as shown in FIG. 1.

In one embodiment of the present disclosure, the protrusions 44 arespaced apart from the bumps 30 and the upper surface 12A by a gap suchas an air gap 46. Furthermore, the projections 42 are spaced apart fromthe top plane 32 of the bumps 30 by the air gap 46. The projections 42,the protrusions 44, the air gap 46, the top plane 32, the wall surfaces34 and the inclined surfaces 36 are configured to scatter and/ordiffract the light beams generated by the light-emitting structure 16 tothe outside of the semiconductor light-emitting device 10. Consequently,the internal total reflection of the light beams in the light-emittingdevice 10 can be dramatically decreased to prevent the light beams frombeing adsorbed by the light-emitting structure 16, so as to improve thelight extraction efficiency.

FIG. 8 is a close-up cross-sectional view along the cross-sectional line1-1 in FIG. 1, and FIG. 9 is a close-up cross-sectional view along thecross-sectional line 2-2 in FIG. 1 according to another embodiment ofthe present disclosure. In one embodiment of the present disclosure, thefirst conductive type semiconductor layer 14 includes a plurality ofprotrusions 44′ each facing a portion of the upper surface 12A of thesubstrate 12 between the bumps 30, the protrusions 44′ are positioned ina ring manner at a peripheral region 40 of the first conductive typesemiconductor layer 14, and the width of the peripheral region 40 isbetween 5 and 10 microns, as shown in FIG. 1. Furthermore, the firstconductive type semiconductor layer 14 may optionally include aplurality of projections (not shown in FIG. 8 and FIG. 9) each facingthe top plane 32 of the bumps 30, similar to the projection 42 shown inFIG. 5.

In one embodiment of the present disclosure, the protrusions 44′ contactthe portion of the substrate 12 between the bumps 30, and are spacedapart from the bumps 30 by a gap such as an air gap 46′. Furthermore,the protrusions 44′, the air gap 46′, the top plane 32, the wallsurfaces 34 and the inclined surfaces 36 are configured to scatterand/or diffract the light beams generated by the light-emittingstructure 16 to the outside of the semiconductor light-emitting device10. Consequently, the internal total reflection of the light beams inthe light-emitting device 10 can be dramatically decreased to preventthe light beams from being adsorbed by the light-emitting structure 16,so as to improve the light extraction efficiency.

In one embodiment of the present disclosure, the air gap 46 or 46′ canbe formed by performing a wet etching process after the epitaxy processof the first conductive type semiconductor layer 14. The etchant of thewet etching process may include hydrofluoric acid, nitric acid,phosphoric acid, base solution, or mixture of base solution and alcohol,which etches the first conductive type semiconductor layer 14 along theinterface between the bumps 30 of the substrate 12 and the firstconductive type semiconductor layer 14. The projections 42 may beremoved by the wet etching process such that the first conductive typesemiconductor layer 14 only has the protrusion 44 or 44′ facing thesubstrate 12.

In one embodiment of the present disclosure, the substrate 12 includestransparent insulation material such as sapphire, silicon, or siliconcarbide; the n-type semiconductor layer 14, the light-emitting structure16 and the p-type semiconductor layer 18 may include III-V materialselected from the group consisting of AlGaN, GaN, InGaN, AlGaInN, GaP,or GaAsP; the contact layer 20 includes III-V material such as such asAlGaN, GaN, InGaN, AlGaInN, GaP, or GaAsP; the transparent conductivelayer 22 includes indium oxide, tin oxide or indium tin oxide; and thelight-emitting structure 16 may include the quantum well ormulti-quantum well structure sandwiched between a p-cladding layer andan n-cladding layer on the n-type semiconductor layer 114. In addition,the n-type semiconductor layer 14, the light-emitting structure 16 andthe p-type semiconductor layer 18 may include II-VI material selectedfrom the group consisting of ZnCdSe, ZnMgSe, ZnBaSe, ZnBeSe, ZnCaSe,ZnSrSe, ZnCdSSe, ZnMgSSe, ZnCdTe, ZnMgTe, ZnBaTe, ZnBeTe, ZnCaTe,ZnSrTe, ZnCdSTe and ZnMgSTe. In particular, the epitaxy machine can beused to prepare these layers on the substrate 12.

In one embodiment of the present disclosure, the top plane 32 is aC-plane (0,0,1) substantially parallel to the upper surface 12A of thesubstrate 12. The preparation of the bumps 30 may include the steps offorming a mask having a plurality of patterns covering a portion of thesubstrate, and performing an etching process to remove a portion of thesubstrate not covered by the mask to form the bumps 30 under thepatterns. In one embodiment of the present disclosure, the etchingprocess is a wet etching process using an etchant including phosphoricacid.

FIG. 10 is a top view of a semiconductor light-emitting device 60according to a second embodiment of the present disclosure, and FIG. 11is a cross-sectional view along the cross-sectional line 3-3 in FIG. 10.The semiconductor light-emitting device 60 comprises a substrate 62, ann-type semiconductor layer 64 positioned on the substrate 62, alight-emitting structure 66 positioned on the n-type semiconductor layer64, a p-type semiconductor layer 68 positioned on the light-emittingstructure 66, a contact layer 70 positioned on the p-type semiconductorlayer 68, a crystal layer 78 positioned on the contact layer 70, atransparent conductive layer 72 positioned on the crystal layer 78, afirst electrode 74 positioned on the n-type semiconductor layer 64, anda second electrode 76 positioned on the transparent conductive layer 72.In one embodiment of the present disclosure, the crystal layer 78includes a plurality of bumps 78A configured to improve the propagationof the light beams from the light-emitting structure 66 to the outsideof the light-emitting device 60 so as to increase the light-emittingefficiency.

FIG. 12 is a full view of the substrate 62 according to the secondembodiment of the present disclosure. In one embodiment of the presentdisclosure, the substrate 62 has an upper surface 62A and a plurality ofbumps 80 positioned on the upper surface 62A in a periodic manner. Thebumps 80 are positioned in a plurality of odd rows and a plurality ofeven rows, and each of the bumps 80 in the even rows is positioned at aninterval between adjacent two bumps 80 in the odd rows. The height ofthe bumps 80 is between 0.5 and 5 microns, the interval between theadjacent two bumps 80 is between 0.5 and 10 microns, and the width ofthe bumps 80 is between 0.5 and 5 microns.

Each bump 80 has a top plane 82, five wall surfaces 84, and threeinclined surfaces 86 sandwiched between the top plane 82 and the wallsurfaces 84, wherein each of the inclined surfaces 86 is between two ofthe wall surfaces 84. The wall surface 84 and the inclined surface 86 ofthe bump 80 have different inclined angles, which is the included anglebetween the upper surface 62A and the wall surface 84 (or the inclinedsurface 86). The wall surface 84 and the inclined surface 86 areconnected, and the included angle between the inclined surface 86 andthe wall surface 84 is between 90 and 180 degrees. In addition, the bump80 has a base surface 88 having five corners, and the connections of thecorners is arc-shaped, i.e., the wall surface 84 is arc-shaped.

FIG. 13 is a close-up cross-sectional view along the cross-sectionalline 3-3 in FIG. 10, and FIG. 14 is a close-up cross-sectional viewalong the cross-sectional line 4-4 in FIG. 10 according to oneembodiment of the present disclosure. In one embodiment of the presentdisclosure, the first conductive type semiconductor layer 64 includes aplurality of protrusions 94 each facing a portion of the upper surface62A of the substrate 62 between the bumps 80. Furthermore, the firstconductive type semiconductor layer 64 may optionally includes aplurality of projections 92 each facing the top plane 82 of the bumps80. In one embodiment of the present disclosure, the protrusions 94 arepositioned in a ring manner at a peripheral region 90 of the firstconductive type semiconductor layer 64, and the width of the peripheralregion 90 is between 5 and 10 microns, as shown in FIG. 13.

In one embodiment of the present disclosure, the protrusions 94 arespaced apart from the bumps 80 and the portion of the substrate 62between the bumps 80 by a gap such as an air gap 96. Furthermore, theprojections 92 are spaced apart from the top plane 82 of the bumps 80 bythe air gap 96. The projections 92, the protrusion 94, the air gap 96,the top plane 82, the wall surfaces 84 and the inclined surfaces 86 areconfigured to scatter and/or diffract the light beams generated by thelight-emitting structure 66 to the outside of the light-emitting device60. Consequently, the internal total reflection of the light beams inthe light-emitting device 60 can be dramatically decreased to preventthe light beams from being adsorbed by the light-emitting structure 66,so as to improve the light extraction efficiency.

FIG. 15 is a close-up cross-sectional view along the cross-sectionalline 3-3 in FIG. 10, and FIG. 16 is a close-up cross-sectional viewalong the cross-sectional line 4-4 in FIG. 10 according to anotherembodiment of the present disclosure. In one embodiment of the presentdisclosure, the first conductive type semiconductor layer 64 includes aplurality of protrusions 94′ each facing a portion of the upper surface62A of the substrate 62 between the bumps 80, the protrusions 94′ arepositioned in a ring manner at a peripheral region 90 of the firstconductive type semiconductor layer 64, and the width of the peripheralregion 90 is between 5 and 10 microns, as shown in FIG. 10. Furthermore,the first conductive type semiconductor layer 64 may optionally includea plurality of projections (not shown in FIG. 15 or FIG. 16) each facingthe top plane 82 of the bumps 80, similar to the projection 92 shown inFIG. 13.

In one embodiment of the present disclosure, the protrusions 94′ contactthe portion of the substrate 62 between the bumps 80, and are spacedapart from the bumps 80 by a gap such as an air gap 96′. Furthermore,the protrusions 94′, the air gap 96′, the top plane 82, the wallsurfaces 84 and the inclined surfaces 86 are configured to scatterand/or diffract the light beams generated by the light-emittingstructure 66 to the outside of the semiconductor light-emitting device60. Consequently, the internal total reflection of the light beams inthe light-emitting device 60 can be dramatically decreased to preventthe light beams from being adsorbed by the light-emitting structure 66,so as to improve the light extraction efficiency.

In one embodiment of the present disclosure, the air gap 96 or 96′ canbe formed by performing a wet etching process after the epitaxy processof the first conductive type semiconductor layer 64. The etchant of thewet etching process may include hydrofluoric acid, nitric acid,phosphoric acid, base solution, or mixture of base solution and alcohol,which etches the first conductive type semiconductor layer 64 along theinterface between the bumps 80 of the substrate 62 and the firstconductive type semiconductor layer 64. The projections 92 may beremoved by the wet etching process such that the first conductive typesemiconductor layer 64 only has the protrusion 94 or 94′ facing thesubstrate 62.

In one embodiment of the present disclosure, the substrate 62 includestransparent insulation material such as sapphire, silicon, or siliconcarbide; the n-type semiconductor layer 64, the light-emitting structure66 and the p-type semiconductor layer 68 may include III-V materialselected from the group consisting of AlGaN, GaN, InGaN, AlGaInN, GaP,or GaAsP; the contact layer 70 includes III-V material selected from thegroup consisting of AlGaN, GaN, InGaN, AlGaInN, GaP, or GaAsP; thetransparent conductive layer 72 includes indium oxide, tin oxide orindium tin oxide; and the light-emitting structure 66 may include thequantum well or multi-quantum well structure sandwiched between ap-cladding layer and an n-cladding layer on the n-type semiconductorlayer 64. In addition, the n-type semiconductor layer 64, thelight-emitting structure 66 and the p-type semiconductor layer 68 mayinclude II-VI material selected from the group consisting of ZnCdSe,ZnMgSe, ZnBaSe, ZnBeSe, ZnCaSe, ZnSrSe, ZnCdSSe, ZnMgSSe, ZnCdTe,ZnMgTe, ZnBaTe, ZnBeTe, ZnCaTe, ZnSrTe, ZnCdSTe and ZnMgSTe. Inparticular, the epitaxy machine can fabricate these layers on thesubstrate 62.

In one embodiment of the present disclosure, the top plane 82 is aC-plane (0,0,1) substantially parallel to the upper surface 62A of thesubstrate 62. The preparation of the bumps 80 may include the steps offorming a mask having a plurality of patterns covering a portion of thesubstrate, and performing an etching process to remove a portion of thesubstrate not covered by the mask to form the bumps 80 under thepatterns. In one embodiment of the present disclosure, the etchingprocess is a wet etching process using an etchant including phosphoricacid.

FIG. 13 is a top view of a semiconductor light-emitting device 110according to a third embodiment of the present disclosure, and FIG. 14is a cross-sectional view along the cross-sectional line 5-5 in FIG. 13.The semiconductor light-emitting device 110 comprises a substrate 112,an n-type semiconductor layer 114 positioned on the substrate 112, alight-emitting structure 116 positioned on the n-type semiconductorlayer 114, a p-type semiconductor layer 118 positioned on thelight-emitting structure 116, a contact layer 120 positioned on thep-type semiconductor layer 118, a crystal layer 128 positioned on thecontact layer 120, a transparent conductive layer 122 positioned on thecrystal layer 128, a first electrode 124 positioned on the n-typesemiconductor layer 114, and a second electrode 126 positioned on thetransparent conductive layer 122. In one embodiment of the presentdisclosure, the crystal layer 128 includes a plurality of depressions128A configured to improve the propagation of the light beamspropagating from the light-emitting structure 116 to the outside of thelight-emitting device 110 so as to increase the light-emittingefficiency.

FIG. 15 is a full view of the substrate 112 according to the thirdembodiment of the present disclosure, and FIG. 16 is a scanning electronmicroscopy image of the substrate 112 according to the third embodimentof the present disclosure. In one embodiment of the present disclosure,the substrate 112 has an upper surface 112A and a plurality of bumps 130positioned on the upper surface 112A in a periodic manner. The bumps 130are positioned in a plurality of odd rows and a plurality of even rows,and each of the bumps 130 in the even rows is positioned at an intervalbetween adjacent two bumps 130 in the odd rows. The height of the bumps130 is between 0.5 and 5 microns, the interval between the adjacent twobumps 130 is between 0.5 and 10 microns, and the width of the bumps 130is between 0.5 and 5 microns.

Each bump 130 has a top plane 132, a ridge portion 140, a plurality ofwall surfaces 134, and a plurality of inclined surfaces 136. The ridgeportion 140 has a plurality of branches 142, the wall surfaces 134 aresandwiched between the branches 142, and the inclined surfaces 136 arepositioned on free ends of the branches 142, with the free ends beingadjacent to the upper surface 112A. In one embodiment of the presentdisclosure, the ridge portion 140 includes three branches 142, and thebump 130 includes three wall surfaces 134 and three inclined surfaces136. The top plane 132 of the bump 130 connects the branches 142, i.e.,the top plane 133 is sandwiched among the branches 142. In addition, thetop plane 132 can be dart-shaped, and the ridge portion 140 is above thewall surface 134.

The wall surface 134 and the inclined surface 136 of the bump 130 havedifferent inclined angles, which is the included angle between the uppersurface 112A and the wall surface 134 (or the inclined surface 136). Thewall surface 134 and the inclined surface 136 are connected, and theincluded angle between the inclined surface 136 and the wall surface 134is between 90 and 180 degrees. The different inclined angles areconfigured to reflect the light beams generated by the light-emittingstructure 116 at different reflection angles. In addition, the bump 130has a base surface 138 having three corners, and the connection of thecorners is arc-shaped, i.e., the wall surface 134 is arc-shaped. Theridge portion 140, the wall surface 134, the inclined surface 136, andthe top plane 132 can reflect the light beams generated by thelight-emitting structure 116 at any angle to the outside of thelight-emitting device 100. Consequently, the repeated internalreflection of the light beams in the light-emitting device 100 isdecreased dramatically to prevent the light beams from being adsorbed bythe light-emitting structure 116, so as to improve the light extractionefficiency.

FIG. 17 is a close-up cross-sectional view along the cross-sectionalline 5-5 in FIG. 13, and FIG. 18 is a close-up cross-sectional viewalong the cross-sectional line 6-6 in FIG. 13. In one embodiment of thepresent disclosure, the first conductive type semiconductor layer 114includes a plurality of protrusions 154 each facing a portion of theupper surface 112A of the substrate 112 between the bumps 130.Furthermore, the first conductive type semiconductor layer 114 mayoptionally include a plurality of projections 152 each facing the topplane 132 of the bumps 130. In one embodiment of the present disclosure,the protrusions 154 are positioned in a ring manner at a peripheralregion 150 of the first conductive type semiconductor layer 114, and thewidth of the peripheral region 150 is between 5 and 10 microns, as shownin FIG. 17.

In one embodiment of the present disclosure, the protrusions 154 arespaced apart from the bumps 130 and the portion of the substrate 112between the bumps 130 by a gap such as an air gap 156. Furthermore, theprojections 152 are spaced apart from the top plane 132 of the bumps 130by the air gap 156. The projections 152, the protrusions 154, the airgap 156, the top plane 132, the wall surfaces 134, the inclined surfaces136, and the ridge portion 140 are configured to scatter and/or diffractthe light beams generated by the light-emitting structure 116 to theoutside of the light-emitting device 110. Consequently, the internaltotal reflection of the light beams in the light-emitting device 110 canbe dramatically decreased to prevent the light beams from being adsorbedby the light-emitting structure 116, so as to improve the lightextraction efficiency.

FIG. 23 is a close-up cross-sectional view along the cross-sectionalline 5-5 in FIG. 17, and FIG. 24 is a close-up cross-sectional viewalong the cross-sectional line 6-6 in FIG. 17 according to anotherembodiment of the present disclosure. In one embodiment of the presentdisclosure, the first conductive type semiconductor layer 114 includes aplurality of protrusions 154′ each facing a portion of the upper surface112A of the substrate 112 between the bumps 130, the protrusions 154′are positioned in a ring manner at a peripheral region 150 of the firstconductive type semiconductor layer 114, and the width of the peripheralregion 150 is between 5 and 10 microns, as shown in FIG. 17.Furthermore, the first conductive type semiconductor layer 114 mayoptionally include a plurality of projections (not shown in FIG. 23 orFIG. 24) each facing the top plane 132 of the bumps 130, similar to theprojections 152 shown in FIG. 21.

In one embodiment of the present disclosure, the protrusions 154′contact the portion of the substrate 112 between the bumps 130, and arespaced apart from the bumps 130 by a gap such as an air gap 156′.Furthermore, the protrusions 154′, the air gap 156′, the top plane 132,the wall surfaces 134, the inclined surfaces 136, and the ridge portion140 are configured to scatter and/or diffract the light beams generatedby the light-emitting structure 116 to the outside of the semiconductorlight-emitting device 110. Consequently, the internal total reflectionof the light beams in the light-emitting device 110 can be dramaticallydecreased to prevent the light beams from being adsorbed by thelight-emitting structure 116, so as to improve the light extractionefficiency.

The air gap 156 or 156′ can be formed by performing a wet etchingprocess after the epitaxy process of the first conductive typesemiconductor layer 114. The etchant of the wet etching process mayinclude hydrofluoric acid, nitric acid, phosphoric acid, base solution,or mixture of base solution and alcohol, which etches the firstconductive type semiconductor layer 114 along the interface between thebumps 130 of the substrate 112 and the first conductive typesemiconductor layer 114. The projections 152 may be removed by the wetetching process such that the first conductive type semiconductor layer114 only has the protrusion 154 or 154′ facing the substrate 112.

In one embodiment of the present disclosure, the substrate 112 includestransparent insulation material such as sapphire, silicon, or siliconcarbide; the n-type semiconductor layer 114, the light-emittingstructure 116 and the p-type semiconductor layer 118 may include III-Vmaterial selected from the group consisting of AlGaN, GaN, InGaN,AlGaInN, GaP, or GaAsP; the contact layer 120 includes III-V materialselected from the group consisting of AlGaN, GaN, InGaN, AlGaInN, GaP,or GaAsP; the transparent conductive layer 122 includes indium oxide,tin oxide or indium tin oxide; and the light-emitting structure 116 mayincludes the quantum well or multi-quantum well structure sandwichedbetween a p-cladding layer and an n-cladding layer on the n-typesemiconductor layer 114. In addition, the n-type semiconductor layer114, the light-emitting structure 116 and the p-type semiconductor layer118 may include II-VI material selected from the group consisting ofZnCdSe, ZnMgSe, ZnBaSe, ZnBeSe, ZnCaSe, ZnSrSe, ZnCdSSe, ZnMgSSe,ZnCdTe, ZnMgTe, ZnBaTe, ZnBeTe, ZnCaTe, ZnSrTe, ZnCdSTe and ZnMgSTe. Inparticular, the epitaxy machine can fabricate these layers on thesubstrate 112.

In one embodiment of the present disclosure, the top plane 132 is aC-plane (0,0,1) substantially parallel to the upper surface 112A of thesubstrate 112. The preparation of the bumps 130 may include the steps offorming a mask having a plurality of patterns covering a portion of thesubstrate, performing an etching process to remove a portion of thesubstrate not covered by the mask, removing the mask, and performinganother etching process on the substrate without the shadowing of themask to form the bumps 130 on the substrate 112. In one embodiment ofthe present disclosure, the etching process can be wet etching processusing an etchant including phosphoric acid.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. For example,many of the processes discussed above can be implemented in differentmethodologies and replaced by other processes, or a combination thereof.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present disclosure, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present disclosure. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

1. A semiconductor light-emitting device, comprising: a substrateincluding an upper surface and a plurality of bumps positioned on theupper surface, each of the bumps including a top plane substantiallyparallel to the upper surface; a first conductive type semiconductorlayer positioned on the substrate, the first conductive typesemiconductor layer including a plurality of protrusions each facing aportion of the substrate between the bumps, and the first protrusionsbeing spaced apart from the bumps; a light-emitting structure positionedon the first conductive type semiconductor layer; and a secondconductive type semiconductor layer positioned on the light-emittingstructure.
 2. The semiconductor light-emitting device of claim 1,wherein the first conductive type semiconductor layer further includes aplurality of projections each facing the top plane of the bumps.
 3. Thesemiconductor light-emitting device of claim 1, wherein the projectionsare spaced apart from the top plane of the bumps by a gap.
 4. Thesemiconductor light-emitting device of claim 1, wherein each of thebumps includes a plurality of wall surfaces and a plurality of inclinedsurfaces sandwiched between the top plane and the wall surfaces, andeach of the inclined surfaces is between two of the wall surfaces. 5.The semiconductor light-emitting device of claim 4, wherein the inclinedsurface and the wall surface have different inclined angles.
 6. Thesemiconductor light-emitting device of claim 4, wherein the inclinedsurface connects to the wall surface, and the included angle between theinclined surface and the wall surface is between 90 and 180 degrees. 7.The semiconductor light-emitting device of claim 4, wherein the wallsurface is arc-shaped.
 8. The semiconductor light-emitting device ofclaim 4, wherein the bump includes a bottom plane having three corners.9. The semiconductor light-emitting device of claim 8, wherein theconnection of the corners is arc-shaped.
 10. The semiconductorlight-emitting device of claim 1, wherein each of the bumps includes aridge portion having a plurality of branches, and the top plane connectsthe branches.
 11. The semiconductor light-emitting device of claim 10,wherein each of the bumps further includes a plurality of wall surfacesand a plurality of inclined surfaces positioned on free ends of thebranches, with the free ends being adjacent to the upper surface. 12.The semiconductor light-emitting device of claim 11, wherein theinclined surface and the wall surface have different inclined angles.13. The semiconductor light-emitting device of claim 11, wherein thewall surface is arc-shaped.
 14. The semiconductor light-emitting deviceof claim 11, wherein the bump includes three inclined surfaces.
 15. Thesemiconductor light-emitting device of claim 10, wherein the bumpincludes three branches.
 16. The semiconductor light-emitting device ofclaim 10, wherein the bump includes a bottom plane having at least threecorners.
 17. The semiconductor light-emitting device of claim 16,wherein the connection of the corners is arc-shaped.
 18. Thesemiconductor light-emitting device of claim 10, wherein the top planeis dart-shaped.
 19. The semiconductor light-emitting device of claim 1,wherein the top plane is a C-plane.
 20. The semiconductor light-emittingdevice of claim 1, wherein the bumps are positioned on the upper surfacein a periodic manner.
 21. The semiconductor light-emitting device ofclaim 1, wherein the substrate is made of a material selected from agroup consisting of sapphire, silicon, and silicon carbide.
 22. Thesemiconductor light-emitting device of claim 1, wherein the bumps arepositioned into a plurality of odd rows and a plurality of even rows,and each of the bumps in the even rows is positioned at an intervalbetween adjacent two bumps in the odd rows.
 23. The semiconductorlight-emitting device of claim 1, wherein the height of the bumps isbetween 0.5 and 5 microns.
 24. The semiconductor light-emitting deviceof claim 1, wherein the interval between the adjacent two bumps isbetween 0.5 and 10 microns.
 25. The semiconductor light-emitting deviceof claim 1, wherein the width of the bumps is between 0.5 and 5 microns.26. The semiconductor light-emitting device of claim 1, wherein thebumps are configured to scatter and/or diffract lights from thelight-emitting structure.
 27. The semiconductor light-emitting device ofclaim 1, wherein the protrusions are configured to scatter and/ordiffract lights from the light-emitting structure.
 28. The semiconductorlight-emitting device of claim 1, wherein the bumps are configured toscatter and/or diffract lights from the light-emitting structure.